1. Field of the Invention
The invention relates to a curing accelerator for a curing resin, a curing resin composition using the curing accelerator, suitable for molding materials, laminated sheet materials or adhesive materials, an electronic component device provided with device components encapsulated with the curing resin composition, and a method for obtaining a phosphine derivative used for the curing accelerator.
2. Description of the Related Art
Curing resins such as an epoxy resin are conventionally used in a wide range as molding materials, laminated sheet materials and adhesive materials. Since these curing resins require rapid curability from the viewpoint of the productivity improvement, compounds for accelerating the curing reaction, that is, curing accelerators are widely used. Of the curing resins, especially, epoxy resin compositions are in wide use in the field of the encapsulation of device components in electronic components such as transistors and ICs. This is because the epoxy resin has properties such as molding properties, electrical properties, moisture resistance, heat resistance, mechanical properties and adhesion to component inserts which are well balanced. Especially, the combination of an o-cresol novolak type epoxy resin and a phenol novolac curing agent excels in these balances, and is preferably used as a base resin for the molding material for IC encapsulation. Amine compounds such as a third amine and imidazole and phosphorus compounds such as phosphines and phosphonium are generally used as the curing accelerator in the epoxy resin compositions.
The high density mounting on printed circuit boards of electronic components has been recently advanced, and, therefore, surface-mounted packages have become mainstream in place of conventional pin inserting type packages in the electronic components. In the surface-mounted ICs such as ICs and LSIs, the occupation volume of the component to the package gradually is increased so as to improve the mounting density, and the thickness of the package has been extremely thin. In the pin inserting type packages, after pins are inserted through the wiring board, soldering is performed from the back of the wiring board, and thereby, the package is not exposed directly to high temperatures. On the other hand, after the surface-mounted type ICs are temporarily attached to the surface of the wiring board, the surface-mounted type ICs are treated by a solder bus and a reflow device or the like, and thereby, the surface-mounted type ICs are exposed directly to soldering temperatures. As a result, when the IC package absorbs moisture, the absorbing moisture expands rapidly at the time of soldering, resulting in the package crack, therefore, this has become the great problem.
So as to improve the reflow cracking resistance to the package crack at the time of the soldering, so-called the flow properties crack, epoxy resin compositions containing a lot of inorganic fillers are proposed. However, since the increasing amount of the inorganic filler causes the decrease in flow properties at the time of molding, faulty filling, faulty conduction due to breaking of bonding wires of IC chips, and the performance of molded products may lower, there is a limit in the increasing amount of the inorganic filler. As a result, this technique can not be expected to bring about any remarkable improvement in the reflow cracking resistance. Particularly, when the amine system curing accelerators such as phosphorus type curing accelerators such as triphenylphosphine, amine type curing accelerators such as 1,8-diazabicyclo [5.4.0]undecene-7 are used, the flow properties is low, and thereby this technique can not be expected to bring about any remarkable improvement in the reflow cracking resistance.
So as to overcome such a problem, it is proposed that an addition product of triphenylphosphine with 1,4-benzoquinone be used as a curing accelerator (see, Japanese Patent Application Laid-Open (JP-A) No. 9-157497). When the addition product is used as the curing accelerator, there is a problem in curability when the resin composition is exposed to air, in a word, curability under moisture absorption. When the molding material having poor curability under moisture absorption absorbs moisture from air at the time of manufacturing, transporting and using, troubles such as gate break, chip crack, the reduction of releasability are easily caused. Also, problems exist in that the difference of the air humidity at the time of manufacturing transporting and using, particularly, and the molding performance is not stable due to the difference of the season. Moreover, a problem in that rapid curability is bad, and the resin composition is not cured in a short time when an organic phospholam compound (see, JP-A No. 11-60906) proposed as a curing accelerator having steady curability is used. So as to overcome such a problem, it is proposed that an addition product of a phosphine compound in which at least one alkyl group is bonded with a phosphorus atom and a quinone compound is used as the curing accelerator (see, JP-A Nos. 2002-3574 and 2002-80563).
However, a problem exists in that when a package encapsulated with the curing resin composition used as the curing accelerator is exposed to high temperature, electrical continuity defect is easily generated in the package, that is, the package has poor high-temperature storage characteristics. The present invention was made taking account of the problems discussed above. It is an object of the present invention to provide a curing accelerator for a curing resin which exhibits superior curability under moisture absorption, flow properties, reflow cracking resistance and high-temperature storage characteristics, a method for obtaining a phosphine derivative used for the curing accelerator, a curing resin composition using the curing accelerator, and an electronic component device having a device component encapsulated with the curing resin composition.